Effects of turnip rape trap crops on oilseed rape pests in a network of organic farmers' fields

摘要

The long-term goal of organic farming is to efficiently manage crop protection against pests, based on an understanding of the biology of the organisms in relation to cropping systems and boundaries of fields. Organic farmers in France hesitate to grow winter oilseed rape because it is attacked by numerous insects, especially Coleoptera, which are difficult to control without chemical treatments. In France, the main insects which caused damage to winter rape are: cabbage stem flea beetle (CSFB) (Psylliodes chrysocephala), rape stem weevil (RSW) (Ceuthorhynchus napi) and pollen beetle (Meligethes anaeus). Some elements of crop management, such as the date of so whig, the soil tillage, plant densities, affects damage caused by these pests (Valantin-Morison et al., 2006) but not sufficiently to manipulate pest attacks on this crop when no pesticide is allowed. Many studies have focused on the effects of host plants on orientation and feeding (Bartlet et al., 2004), oviposition behaviour (Borg & Ekbom,1996), and egg production of pollen beetle (Hopkins & Ekbom, 1999). Turnip rape (Brassica rapa) has been found to attract pollen beetle under both laboratory and field conditions (e.g. Cook et al., 2002). Parasitoids and predators of pollen beetle havealso been identified (Biichi, 2002) and appear to be affected by host plant (Billqvist & Ekbom, 2001). Recently, control strategies on insect pests of winter rape have been developed in experiments by Cook et al. (2002) and Barari et al., (2005). However, the system has not been tested on diverse farmer's fields hi contrasting climatic conditions. This study investigates the potential use of turnip rape as a trap crop to control insect pests on organic winter rape in a geographically broad network of farmers' fields.